The mobile opportunity gap — or the gap between the share of time consumers spend on mobile devices and the share of ad dollars that is spent on mobile inventory — narrowed considerably in 2015, according to the latest Mary Meeker slide deck from Kleiner Perkins Caufield Byers that debuted at yesterday's Code Conference.

The deck reveals that consumers spent 25% of their time accessing media on mobile devices in 2015. US advertisers, meanwhile, spent only 12% of their ad budgets on mobile inventory during the year. While there is still a significant gap between time spent and ad spend on mobile, the gap has narrowed. In 2014, consumers spent 24% of their time on mobile, but advertisers only spent 8% of their budgets on mobile inventory.

The mobile gap exists for several reasons. While consumers spend more time than ever on mobile devices, it has taken longer for brands to fully embrace mobile ads. The poor performance of traditional digital ad formats (namely banners), a lack of reliable user analytics and tracking capabilities, as well as the increased threat of ad fraud and viewability issues initially stifled the growth of mobile ad spend relative to time spent on the devices.

However, this gap is narrowing as digital players address these issues. Big social mobile platforms with their enormous audiences, like Facebook and Twitter, have eased brands with large ad budgets into mobile.

Companies like Verizon, which owns major ad network AOL, have helped route marketers that are more comfortable with spending on traditional TV to experiment with mobile or cross-device campaigns.

Finally, new platforms like Snapchat have encouraged advertisers to spend big on new innovative mobile-optimized formats like vertical video and interactive ads.

Native ads — or ads that take on the look and feel of the content surrounding them — have been rising in popularity and are taking over digital advertising.

By 2021, native display ad revenue in the US, which includes native in-feed ads on publisher properties and social platforms, will make up 74% of total US display ad revenue, up from a 56% share in 2016, according to new BI Intelligence estimates based off historical data from the Interactive Advertising Bureau (IAB) and PwC, as well as IHS.

The rapid uptick in native's share of display ad revenue can largely be attributed to the dominance of social platforms like Facebook and Twitter — which were early champions of native and rely almost entirely on native formats — as well as the introduction of new programmatic technologies that are making it easier for publishers and advertisers to scale native campaigns.

Margaret Boland, research analyst for BI Intelligence, Business Insider's premium research service, has compiled a detailed report on native advertising that breaks out native ads into three categories: social native, native-style display, and sponsored content (also referred to as premium native). It provides forecasts for how revenues from these formats will grow over the next five years and looks at what factors, in particular, are driving up spending on each of these ad units. As a note, because revenues from these three types of native content can overlap, it does not provide an overall native forecast. Finally, it lays out some of the challenges that face properties that rely on native ads, namely ad frequency and scalability issues.

Here are some key takeaways from the report:

Native-display ads, including social native and native ads in-feed on publisher websites, will make up the bulk of native ad revenue from 2016-2021. Native display ad revenue in the US will rise at a five-year compound annual growth rate (CAGR) of 17% during this time period to eclipse $36 billion. The rise of native video ads, particularly on social platforms, will be one of the main drivers of this growth.

Social platforms generate most of their revenue from native ads and will continue to dominate overall native ad spending through 2021. The dominance of social platforms like Facebook, Instagram, Twitter, and Snapchat on mobile devices, where the entire experience is within a feed, will help propel social's contribution to overall native ad revenue through 2021.

Sponsored content, which is categorized separately from native-display due to the direct relationship between publishers and brands in creating the format, will be the fastest-growing native format over the next five years. However, the high cost to produce these ads and the limitation in inventory will limit the format.

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